This invention relates to multibeam antenna systems for cellular radio applications and, more particularly, to antenna placement for improved space/angle diversity. Use of various types of cellular radio systems is increasing. For reasons including overall cost and also antenna site availability, the effective coverage area of a given cellular site is increasingly important. For many applications, improvements in both coverage area and signal processing can be obtained by using a plurality of beams (e.g., eight beams) of relatively narrow beamwidth (e.g., about 45 degrees beamwidth) to provide omnidirectional coverage (i.e., 360 degrees in azimuth), instead of relying upon a single omnidirective antenna for such purpose.
For improved signal processing, with decreased loss of signal or blind spot degradation, space diversity in antenna placement has been employed in cellular antenna systems. Typically, this has been accomplished by physically displacing one group of antennas from another group, with both groups covering the same sector. Angle diversity, wherein antennas of a first group providing coverage of a sector are aimed at different azimuth angles than antennas of another group covering the same sector, has also been described for use alone or with space diversity placement.
In prior implementation of space diversity, groupings of antennas separated by 10 to 20 feet, omnidirectional antennas mounted on the sides of tower structures, or other less than optimum arrangements have been employed to achieve physical separation of antennas.
Objects of the present invention are, therefore, to provide new and improved cellular antenna systems enabling operation with improved space/angle diversity. Additional objects are to provide cellular antenna systems having one or more of the following characteristics or capabilities:
improved space diversity operation with single mast antenna mounting; PA1 improved angle diversity operation with single mast antenna mounting; PA1 improved space/angle diversity with single mast antenna mounting.